Building a casita in Mesa, Arizona

How the state ADU law applies in Mesa

Mesa has a population well above 75,000, so it's covered by Arizona's new state ADU statute. That means the city is required to allow, on any single-family lot:

• At least one attached accessory dwelling unit (part of your existing home).
• At least one detached accessory dwelling unit — a true backyard casita.
• A third detached ADU on lots of one acre or more, if one unit is deed-restricted affordable.

The baseline Mesa must follow

• Size: up to 1,000 sq ft on lots ≤ 10,000 sq ft; the lesser of 3,000 sq ft or 10% of net lot area on larger lots — and never more than 75% of the main home's gross floor area.
• Setbacks: Mesa cannot require setbacks greater than 5 feet.
• Parking: Mesa cannot require additional off-street parking beyond what the primary home has.
• Owner-occupancy: Mesa cannot require you to live in the main house.
• Materials: Mesa cannot require exterior materials that match the primary dwelling.
• Height / coverage: Mesa cannot impose stricter height or lot-coverage limits on the ADU than on the primary home.

Mesa-specific rules

• Mesa allows internal, attached, and detached ADUs by right in all single-residence districts — no special hearing needed.
• One attached and one detached ADU per lot, regardless of zoning district. A third detached ADU is possible on parcels of 1 acre or more with an affordable deed restriction.
• Five-foot side and rear setbacks.
• Size is capped at 75% of the primary home or 1,000 sq ft, whichever is less.

The queue is short in Mesa right now

Adoption is real but modest: Mesa issued 29 ADU permits in the first eight months of 2025, on pace to beat 2024's total of 30. That's an advantage for early movers — plan review isn't backlogged the way it can be in Phoenix or Scottsdale. If you're ready to build, you're not fighting a line.

A landscaping rebate that pairs well

Mesa's grass-to-xeriscape rebate (up to roughly $2,100 with the SRP match) can offset some of the yard rework a backyard casita usually requires. Not a huge line item, but worth applying for if you're already tearing out turf for the pad.

What a Mesa casita costs

Mesa tracks the metro Phoenix baseline: roughly $150 to $300+ per square foot, with most detached builds landing between $150,000 and $300,000 all-in. Read the full Arizona casita cost guide, then look at how to pay for it in the financing guide.

What still varies by city

Even though the state sets the baseline, Mesa's specific permit process, submittal checklist, plan-review timeline, and impact fees are set locally. Building codes, mechanical requirements, and utility connection rules are also administered by Mesa and its utility providers. Confirm the details with the Mesa planning department before you sign anything with a builder.

HOAs still matter in Mesa

Big chunks of Mesa sit inside HOA-governed neighborhoods. The state ADU law does not override private HOA covenants (CC&Rs). Read yours before you start. Our HOA rules page walks through exactly what to look for.

Practical steps for Mesa homeowners

• Pull your CC&Rs and confirm your neighborhood permits detached ADUs (or that you have no HOA).
• Call Mesa planning and ask for their current ADU submittal checklist under the new state statute.
• Get a survey. Setbacks are 5 feet minimum — no guessing.
• Line up financing before you commission plans. See our financing guide.
• Get at least two contractor bids with itemized scope.

What a casita costs in Mesa

Costs in Mesa track the metro Phoenix baseline: roughly $150 to $300+ per square foot, with most detached builds landing between $150,000 and $300,000 all-in. Utility runs, site conditions, HOA design requirements, and contractor overhead drive most of the variance. Read the full Arizona casita cost guide.